There is hereby appropriated from the motor vehicle fund to the department of transportation for the biennium ending June 30, 1981, the sum of ten million dollars, or so much thereof as may be necessary, to carry out the provisions of RCW 47.10.790: PROVIDED, That the money available for expenditure under this appropriation may not exceed the amount of money derived from the sale of ten million dollars of bonds authorized by RCW 47.10.790 and deposited to the credit of the motor vehicle fund.